The present invention relates generally to an improved wafer cleaning system that employs megasonic energy to clean semiconductor wafers, compact discs, glass wafers, and the like. More specifically, the invention relates to methods and apparatuses configured to protect a fragile component (e.g., quartz, ceramic or sapphire plate, etc.) employed within a megasonic tank.
Semiconductor wafers are often cleaned (individually or in a batch) within a tank of megasonically energized fluid. Such megasonic tanks may employ a plurality of rollers configured to support a wafer and further configured to rotate a wafer, a transducer coupled to the tank""s fluid and configured to direct sonic energy through the fluid to the surfaces of a wafer supported therein. The chamber may further employ a window comprising a plate (e.g., a quartz, sapphire or ceramic plate) configured to cover the transducer such that the transducer(s) may be mounted outside the tank and may transmit energy through the plate to the tank fluid or, such that any transducers contained within the tank are sealed from the tank""s fluid via the plate. Typically the plate and the transducers are positioned along the tank""s bottom wall.
During tank assembly and/or during routine maintenance of the megasonic tank, a technician may be working in the tank with various hand tools while installing, replacing, or adjusting a component of the megasonic tank, such as the rollers, etc. While performing such manual tasks, the technician may accidentally drop a tool (e.g., a screwdriver). Unfortunately, when a hand tool is dropped into or within a megasonic tank, the hand tool may strike and break the plate that covers the transducer. Similarly, the plate may also be broken by falling wafers, which may be manually dropped or may fall, when automated wafer handlers are being calibrated or aligned, etc.
Accordingly, a method and apparatus is needed to reduce the occurrence of plate breakage.
The present invention provides a method and an apparatus that comprises a barrier configured to protect a fragile component from impact by falling objects. The method comprises providing a chamber configured to clean a substrate, and having a fragile component contained therein; and, above the fragile component, installing a barrier that extends over at least the width of the fragile component so as to protect the fragile component from impact by falling objects. The apparatus may comprise a tank configured to contain a liquid. The tank may have an opening configured to allow a substrate to enter the tank from a position above the tank; and may contain a fragile component (e.g., a transducer or a quartz, ceramic or sapphire plate) positioned within the footprint of the opening and configured to transmit sonic energy. The apparatus further comprises a barrier that extends above at least the width of the fragile component.
In one aspect, the inventive apparatus may comprise a megasonic tank having a fragile plate contained in (or forming a window in) the tank, and a barrier that covers at least portions of the width of the fragile plate, so as to protect the plate component from impact by falling objects.
In aspects wherein the barrier is positioned between a substrate supporting location and wherein the fragile component comprises a transducer or a fragile plate through which a transducer transmits energy to a substrate, the barrier thickness is chosen to be a multiple of one half the wavelength of the rate at which the sonic energy (e.g., the sound output by the transducer as the sonic energy) travels through the barrier material (or is otherwise chosen so as to be transparent to the acoustic energy output by the transducer).
Other features and aspects of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.